to reduce liquid

It sounds like you haven't strained it yet. I strain mine and then reduce. It's much easier to see what's going on when the bones and veggies are strained out. If time allows, I also let it sit overnight in the fridge first, peel the fat off and then reduce it.

I would say just simmer it uncovered until it's down to your desire volume.

Hi Susan! What's the question exactly? You need to reduce that amount of stock? I hope to help if you can clarify!